Let me tell you why I think the scenario is unrealistic . The U.S. Army would bring up what ever ordinance that was necessary to blast the sniper from his hole . A sniper is only safe as long as his position is unknown . If it would have been necessary to bring up 8" arty that's what would have happened . Remember this is the Armed Force that coined the term reconnaissance by fire . I can cite a few historical examples in the pacific , mind you , where 155 mm guns were used just for this purpose . Read "With The Old Breed" ,by Eugene Sledge .
the sniper was surounded, and cut off from any chance of escape, it wasent like he could sit there, snipe a couple ppl. then run to the safety of his own army. he was trapped.
im guessing this fact was he reason why the soldiers gave the sniper a chance to surrender peacefully, but like i said. he shot the messenger right infront of the windmill.
now, at the time the messenger got shot, they most likely didnt know wether he was dead or alive at the time.
would you really want to start shelling that position when you had a shot messenger/friend who could possably of been alive so close to it?